Method of metal drilling



E. E. MARTIN ETAL METHOD 0F METAL DRILLING June 23, 1959 med oct. 2s. 195e s vsmeets-shmn 1 1N VEN TORS.

BMM

rraeA/Eys June 23, 1959 E. E. MARTIN ETAL 2,891,426

' METHOD oF METAL DRILLING Filed 001.. 23, 1958 3 Sheets-Sheet 2 0,/ ya 1G03:

F'GO 3a 45 IN V EN TOR.

E. E. MARTIN ETAL METHOD oF METAL DRILLING June 23, 1959 3 Sheets-Sheet 5 Filed oct. 2s. 1958 lia. 6'.

'S 'j' /l A J!! J gli" INVENTORS.

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METHOD OF METAL DRILLING Earnest E. Martin, Glendora, and Ralph W. Walsh, Westminster, Calif.; said Martin assiwor to Ralph W. Walsh, Los Angeles, Calif.

Application Getober 23, 1958, Serial No. '769,170

16 Claims. (Cl. 77-5) This invention relates generally to improved methods for metal drilling and like operations employing rotary drilling or cutting tools in forming enlarging or threading holes within or through metals, ferrous and non-ferrous, alloys thereof, and of which all various kinds of steel, non-ferrous metals such as aluminum, manganese, copper, titanium and their alloys, are illustrative.

More particularly the invention is directed to the solution of major problems arising because of the cutting action of the tool, and Iwhich in the usual past practices have been responsible for certain undesirable cutting effects on the metal as well as adverse efects on the tool itself. One of these problems, encountered in metal drilling, has been the inability in practical commercial operations to drill through various metals, e.g. sheet or plate stainless and other steels, without forming and leaving burrs at the drill exit iside of the hole. Other problems have arisen because of excessive heating of the tools such as drills or taps, that impair their efciency and life. The present invention affords a practical solution of these as well as related problems, in being productive of 'a cutting action of the tool that eliminate such burr formation, preserves accuracy in the hole size, and maintains the tool in a cool condition that obviates the disadvantages to the work and tool that are caused by excessive heating. Because of the importance of being able to drill under such conditions to the elimination of troublesome burr formations, the invention will be described typically as applied to that particular objective.

ln ordinary metal drilling, the drill is axially advanced into or through the metal and rotated by a drive (eg. from a constant speed motor through the customary speed reduction) which requires during the drilling operation, constant speed rotation of the drill under constant driving force. Thus the cutting edge of a drill is given no alternative against following unyieldingly a spiral cutting path dictated in part by manually or mechanically forced axial advancement of the drill. The result is formation of relatively extended segmental spiral cuttings corresponding to extended continuous cutting penetrations of the metal by the drill. The heat generated being a function of the extent and continuity of cutting, the drill thus becomes subjected to temperatures which often necessitate uid cooling of the drill. A further incident of the manner in which the drill cuts, and the kind and extent of the cuttings formed, is the tendency of the drill in finally penetrating the metal, to leave or lay back a partially or fully circular burr, which for many manufacturers, particularly in the precision category, cannot be tolerated. Consequently, presence of the burr entails a further removal operation, sometimes at expenditures of time and money approaching the drilling costs.

In avoiding burr formation and achieving the additional benefits in metal drilling as outlined above, we depart from the customary methods of powering the drill in respects partly characterized in terms of end result, by the action` and elect of the drill to produce United States Patent ECC comminuted small aky or powdery cuttings, as distinguished from from curls or apparent spiral segments. While all the reasons underlying the formation of our line aky cuttings are not fully understood, they apparently result from either or a combination of two principal conditions to which the drill is subjected: (l) maintenance of such rotational lost-motion or slippage in the drill drive as will give the drill a rotationally cushioned or yielding cutting penetration of the metal, and (2) a torque or rotational impulsing of the drill while holding it against axial retraction from its cutting path.

In this latter respect the invention is to be distinguished from prior proposals to comminute the chips or cuttings in metal drilling by axially reciprocating the drill during its continued rotation, in effect by varying the constancy or sustained magnitude of the axial feed. To gain advantages of torque or rotational pulse or vibration eifects to serve the purposes of our invention, we positively hold the drill against axially retractive movement and coniine any pulse effects to the application of drilling torque.

As applied to forms of drilling equipment comprising the combination of an upper rotatable power source drive positively as constant speed, a spindle below, and a drill carried by the spindle, the invention contemplates creating in the drive, as between said power source and the spindle, a capacity for slippage that will result in rotation of the drill at speeds sufficiently slower than the power source to aiiord a full range of necessary cushioned or yielding penetration of the drill into the metal. And this same range may be such as to facilitate use or creation to best advantage of torque impulses to the drill.

A further important object of the invention is to impart to a metal cutting tool such as a drill or thread tapping tool a cushioned or yielding cutting action by the transmission of the drive through a fluid medium in which slippage occurs, thus rendering the tool rotation impositive in accordance with the slippage. With respect to imparting torque pulses to the tool, the invention contemplates creation of such impulses within or in direct relation to the Huid transmission, or independently thereof. Thus we may employ a fluid coupling so designed as to create and transmit to the driven element, rotative pulses or vibrations, or the pulsing may be applied to the driven element extraneously of the fluid coupling proper.

All the features and objects ofthe invention, as well as the details of certain illustrative embodiments, will be fully understood and explained to better advantage in the following description of the accompanying drawings, in which:

Fig. 1 is a view showing in side elevation a typical apparatus embodiment of the invention in the form of a drill press;

Fig. 2 is a cross-sectional plan taken on line 2--2 of Fig. l;

Fig. 3 is a view showing in section certain of the driving and driven parts of the apparatus appearing in Fig. 1;

Fig. 3a is a fragmentary section on line '3a-3a of Fig. 3;

Fig. 4 is an enlarged section on line 4-4 of Fig. 3;

Fig. 5 is a fragmentary enlargement ofone sectional side of the fluid coupling housing;

Fig. 6 illustrates a variational form of the invention in the showing of an enlargement of the iluid coupling and `associated mechanical tool pulsing mechanism;

Fig. 7 is a view showing in enlarged vertical section the pulsing mechanism; and

Fig. 8 is a cross-section on line 8 8 of Fig. 7.

It is to be understood that apparatus adapted to serve the objects and purposes of the invention discussed in the foregoing, may take various specific forms, and that the showing herein of the general aspects of a conventional drill press, but modified and altered to function in. accordance with the invention, is to be regarded as illustrative only.

Referring to Fig. 1, the invention is shown to be embodied typically in a conventional drill press assembly comprising the usual post or standard carrying the vertically adjustable table 11 on which is placed the work metal 12. As illustrative, the work metal may consist of a plate through which one or more holes are to be drilled so that the drill will pass through the plate into the block 13 below. Standard 10 may carry the usual head frame structure 14 including the lower horizontal arm 15 through which a later described spindle extends and within which the spindle is journaled, the frame assembly 14 also including an upper housing 16 for accommodation of parts driven by the head-mounted motor 17. As in the usual drill press, the motor shaft 18 carries differential size pulleys or sheaves 19 for selectively driving through belt 29, a shaft 21 carrying a reverse arrangement of sheaves 22, so that by selection of the driving and driven sheaves, shaft 21 may be driven at different speeds. The sheave assembly 22 is shown in Fig. 3 to be iournaled on bearings 23 and to besplined at 24 to the shaft 21, so that the latter during rotation may be axially advanced to feed the drill into the metal. The feed may be accomplished manually, as by the usual pinion 25 rotatable by hand lever 26 and meshing with rack teeth 27 on sleeve 2S iixed to the shaft 21, or we may use an automatic or mechanical feed as generally indicated at 29.

The mechanical feed is shown to comprise a gear 30 on shaft 31 carrying a pulley 32 driven by belt 33 from a transmission 34 powered by motor 35, the output speed of the transmission being variable by control lever 36. Gear 30 drives spur gear 37 carried by shaft 38 journaledin bearings 39 and threaded at 40 to drive a split nut 41V of the known type releasable by handle 42 from driven engagement With the shaft threads. Thus by selective operation or control of the handles 26 and 42, the drill feed may be either manual, or automatic at mechanically driven constant speed, the rate of which is controllable by the setting of the lever 36. As will be apparent, while the drill is being mechanically advanced, lever 36 is left free and the pinion 25 idles.

Fixed to the lower end of sleeve 28 by clamp bolt 44 and movable vertically with the sleeve, is a U-shaped bracket frame 45 which mounts the split nut 41 and its operating handle 42, and contains an opening 46 through which the shaft 36 passes. The lower arm of bracket 45 supports at 47 the drill spindle 48, the latter being journaled for rotation within radial and axial thrust bearing 49 and held against appreciable axial movement by ring 5 0 fixed to the spindle and bearing upwardly against bearing 49, and flange or ring 51 on the upper end of the spindle engageable downwardly against bearing sleeve 52 fixed within the bracket arm above the bearing. It is significant to note at this point that by reason of the described journaling of the spindle within the bracket arm, the spindle, 4and therefore the drilling or cutting tool, is held against axial retraction from its cutting path within the work metal.

The spindle 48 is driven by shaft 21 through a lostmotion coupling generally indicated at 53, the characterization lost-motion being given the coupling in that it permits infinitely variable 360 degree slippage in the drive and causes working rotation of the spindle at a slower speed than the drive above, within a range of speed differential allowing variations or impulsing of the rotative metal cutting speed of the drill. Otherwise regarded, the coupling 53 so cushions the drive transmission to the drill as to permit of yield in the rotational driving force uthat will enable the drill, in turn, to have a degree of yield in its rotational cutting action in the metal, While the drill is being held against axial retraction from its cutting path.

Highly satisfactory results have been achieved by the employment of a fluid coupling at 53, shown typically to comprise a housing 54 having upper and lower sections 55 and 56 interconnected at 57, the lower section being attached by screws 58 to the upper endl of the spindle 48 so that the housing rotates bodily with and at the same speed as the spindle. The lower section 56 of the housing contains a dished rotor 59 having clearance at 60 from the housing and containing bottom openings 61 which permit oil or other hydraulic tiuid contained in the housing to occupy the clearance at 60 as well as the inside of the rotor to a degree depending upon the quantity of fluid used. The rotor 59 has an integral shaft 62 counterbored to receive a liner bearing sleeve 63, the shaft extending upwardly through bearing sleeve 64 carried by the housing and through an appropriate seal such as O-ring 65 held in place by retaining ring 66. The upper tubular end of shaft 62 carries a xed iiange 67 which is driven by iiange 68 on the lower end of shaft 21 through pins 69 carried by the driving ange and slidable within openings 70 in flange 67. Thus, the tool rotative drive is transmitted from shaftv 21 through pins 69 to the rotor 59, and thence frictionally through the iiuid contained in the housing 56, to the housing and the spindle 48. The tubular upper end of shaft 62 is laterally supported by trunnion 681 projecting integrally from flange 68 within the bearing sleeve 63.

The upper section 55 of the housing may contain a circular arrangement of uniformly spaced vanes 72 having narrow, variable clearance at 73 from similar radial vanes '74 in the rotor 59. The housing and rotor vanes may correspond in number and uniform spacing, or they may vary relatively in number. We haveused satisfactorily a coupling assembly constructed as shown, in which the housing contains eighteen vanes 72, and the rotor nineteen vanes 74, the housing having an internal diameter of about 61A. The rotor. 59 is accommodated for vertical oating movement in the housing, typically within a range of one-hundred and ninety thousandths inch, by maintaining that degree of clearance at 75 between thet upper end of the shaft 62 and the bottom face of the iiange 68. Thus during rotation, the rotor may iioat vertically within this range to a degree dependent upon such factors as the rotative speed and quantity of hydraulic uid in the housing, with consequent variance of the clearances at 60 and 73.`

In actual practice, We have obtained satisfactory results by so governing the operationof the iiuid coupling as to maintain during drilling a spindle speed of around percent of the rotative speed of the drive shaft 21. Depending upon particular conditionstof drilling or tapping, the relative spindle speed may range typically within 70 to 90 percent of the drive shaft speed. Governing of the relative speeds may be effectedin accordance with the quantity of hydraulic liuid put into the coupling, in relation to the speed of the driving shaft 21. Thus, for drive speeds within the range of from 18 to 4800 r.p.m., we may use between about 11/2 and 7ozs. of hydraulic fluid, the iesser quantities of the fluid being used at the higher drive speeds. As will be understood, the drive transmission occurs by reason of frictional transmission through the iiuid within thetclearance space 60, and particularly as the fluid is centriiically thrown outwardly into the narrowing,clearance,and additionally Where quantity of hydraulic iiuid is suiiicient to occupy at least some of the vane clearance` at 73; by reason.

of the iluid frictionaltransmission at this location. It is contemplated that the effect or relation ofthe vanes may be such as tocause creation and transmission through the housing to the spindle, of. rotationallyrpulsing effects as the vanes pass each other. As4 will.;appear, it is also contemplated that pulse effects may be obtained additionally or otherwise, and independently of any pulsing effects created by relative passage of the vanes.

Figs. l and 2 illustrate one method for rotationally impulsing the tool independently of slippage conditions within the iluid coupling. Here the upper section of the housing 55 is shown to carry a plurality of equally spaced radial vanes 76, typically eight in number, against which is directed during drilling, a high velocity air jet from nozzle 77 carried by the bracket 45. The resistance presented by the air jet intermittently to the housing rotation as the yvanes are rotated in the direction of the arrow successively into the path of the air stream, produces rotational impulsing of the cutting tool at a frequency in accordance with the rotative speed and number of vanes.

Figs. 6 to 8 illustrate a variational method and means for rotationally irnpulsing the tool, in this instance by imposing intermittently and mechanically applied restraint to the spindle rotation by means of the detenting mechanism generally indicated at 78. The latter is shown to comprise a circular body 79 containing a plurality, typically eight, of radial bores 80 each containing a liner cylinder 81 within which reciprocates a detenting piston 82 carrying a seal ring 83. Each cylinder carries at its outer end a cap 84 through which iiuid pressure against the piston is maintained by way of a tubular connection 85 with the manifold 86 maintained constant, though variable, air pressure through` connection 87 forming suitable compressed air supply source, not shown. A The body 79 has a central bore 88 through which the spindle 48a extends, the body assembly being held in fixed relation to the spindle axis by bracket 90 attached at 91 to the underside of the bracket frame 45. The spindle is journaled within bearings 92 and 93 within cover plates 94 and 95 secured to the body. Fixed to the spindle within the body bore 88 is a. sleeve 96 carrying a cam node 97 engageable as the spindle rotates, successively against the rounded inner ends 98 of the plungers 82 to displace each plunger successively and outwardly Afrom its riding engagement with the sleeve surface 99, against the resistance air pressure applied to the outer end of the plunger. Thus the transient resistances to the spindle rotation resulting from successive displacements of the plungers, tends to correspondingly retard, and in effect, impulse the cutting rotation of the tool.

Referring again to Fig. l, the spindle 48 is shown to carry below the arm 15 a suitable tool holding means such as a conventional chuck 100, within which is held the tool 101. Where the purpose of the metal cutting is to drill through the work 12, the tool 101 may be a standard metal drill, typically up to 3/s" size, requiring no special modifications in order to accomplish drilling with powdery chip formation and to the complete elimination of any residual burr at the bottom of the hole drilled through the metal. As previously indicated, the described equipment has been found desirable also for thread tapping purposes utilizing instead of a drill, a standard tapping tool.

By reason of the described conditions imparting an essentially yielding or cushioned drive to the tool, and within a speed range below that of the drive shaft 21 permitting tiexibility to the tool as it encounters the resistance of the metal to cutting, the effect of the tool, drill or tap, is to produce powdery or ine flaky cuttings, formation of which occurs throughout the advancement of the drill through the metal, so that ultimately no burr appears at the exit side. As a further consequence of the discontinuity of the cutting action of the tool, the latter is found to remain cool to the extent of eliminating all temperatures that could be detrimental to the life or efficiency of the tool. Finally, it may again be observed that these results tiow from controlling in the manner described, the rotational cutting action of the tool while maintaining steady axial advancement of the 6 tool so that it has no significant axial retraction throughout the course of its cutting travel.

We claim:

1. The method of operating a rotary cutting tool in metal to produce comminuted chip-like cuttings, that includes rotatably driving the tool into the metal from a rotative power source through a rotationally yielding medium and at an infinitely variable rate within a speed range slower than the power source, and simultaneously rotationally impulsing the drill.

2. The method of operating a drill in metal to produce comminuted chip-like cuttings, that includes rotatably driving the drill into the metal from a rotative power source through a rotationally yielding medium at an iniinitely variable rate within a speed range slower than the power source, simultaneously rotataionally impulsing the drill, and maintaining the drill against axial retraction in its cutting path.

3. The method of operating a drill in metal to produce comminuted chip-like cuttings, that includes rotatably driving the drill into the metal from a rotative power source through a uid medium at an infinitely variable rate within a speed range slower than the power source, and simultaneously rotationally impulsing the drill.

4. The method of operating a drill in metal to produce comminuted chip-like cuttings, that includes rotatably driving the drill into the work metal from a rotative power source through a centrifugally displaced body of liquid at an inlinitely variable rate within a speed range slower than the power source, simultaneously rotationally impulsing the drill, and maintaining the drill against axial retraction in its cutting path while vertically supporting the drill independently of the work metal.

5 The method of operating a drill in metal to produce comminuted chip-like cuttings, that includes rotatably driving the drill, advancing the drill into the metal while positively maintaining the drill against axial retraction in its cutting path, and simultaneously rotationally impulsing the drill by rotating the drill against plural resistances per revolution imposed independently of the work metal.

6. The method of advancing a drill through a body of metal, that includes forming comminuted chip-like cuttings and a hole that is burr-free at the drill exit end by rotatively driving the drill through the metal from a rotative power source through a rotationally yielding medium imparting yieldability to the drill in its cutting approach to the metal, simultaneously rotationally impulsing the drill, and simultaneously supporting the drill in both axial directions independently of the work metal.

7. The method of advancing a drill through a body of metal, that includes forming comminuted chip-like cuttings and a hole that is burr-free at the drill exit end by rotatively driving the drill through the metal from a rotative power source through a rotationally yielding iuid medium, imparting yieldability to the drill in its cutting approach to the metal and drill rotation at iniinitely variable rates slower than said power source, axially supporting the drill independently of the work metal and maintaining the drill against axial retraction in its cutting path, and simultaneously rotationally impulsing the drill.

8. The method of advancing a drill through a body of metal, that includes forming comminuted chip-like cuttings and a hole that is burr-free at the drill exit end by rotatively driving the drill through the metal from a rotative power source while maintaining the drill against axial retraction in its cutting path, simultaneously rotationally impulsing the drill, and simultaneously supporting the drill in both axial directions independently of the work metal.

9. The method of advancing a drill through a body of metal, that includes forming comminuted chip-like cuttings and a hole that is burr-free at the drill exit end by rotatively driving the drill into the metal from a rota tive power source, positively and uninterruptedly feeding the drill through the metal, simultaneously rotationally impulsing the drill, and simultaneously supporting the drill in both axial directions independently of the work metal.

10. The method of operating a rotary cutting tool in metal to `produce comminuted chip-like cuttings, that includes creating a rotational drive, transmitting the drive through a rotationally yielding medium and at a slower iniinitely variable rate to rotate the tool, creating cnnstant rotational slippage in said medium throughout 369 degree relative rotation of the drive and drill whereby the tool during drilling is maintained free for rotational pulsing, advancing the tool into the work metal, and axially supporting the tool independently of the work metal.

11. The method of operating a rotary cutting tooi in metal to produce comminuted chip-like cuttings, that includes creating a constant speed rotational drive, transmitting the drive through a rotationally yielding medium and at a slower innitely variable rate to rotate the tool, creating constant rotational slippage in said medium throughout 360 degree relative rotation of the drive and drill whereby the tool during drilling is maintained free for rotational pulsing, advancing the tool into the work metal, and axially supporting the tool independently of the Work metal while positively blocking the tool against axial retraction in its cutting path.

12. The vmethod of operating a rotary cutting tool in metal to Vproduce comminuted chip-like cuttings7 that includes creating a rotational drive, transmitting the drive through a rotationally yielding body of uid and at a slower infinitely variable rate to rotate the tool, creating constant rotational slippage in said medium throughout 360 degree relative rotation of the drive and drill whereby the tool during drilling is maintained free for rotational pulsing, advancing the tool into the work metal, and axially supporting the tool independently of the work metal.

13. The method of operating a rotary cutting tool in metal to produce cornminuted chip-like cuttings, that includes creating a rotational drive, transmitting the drive to the tool through a rotationally yielding medium and at a slower infinitely variable rate within a range of about 70% -to 90% of the rotational drive speed, creating constant rotational slippage in said medium throughout 360 degree relative rotation of the drive and drill whereby the tool during drilling is maintained free for rotational pulsing, advancing 4the tool into the work metal, and laxially supporting the tool independently of the work metal.

14. The method of claim 13, in which said yielding medium comprises -a non-magnetic liquid.

15. The method of advancing a drilling tool through a body of metal, that includes forming comminuted chipf like cuttings and a hole that is burr-free at the-drill exit end by creating a rotational drive, transmitting the drive through a rotationally yielding medium and at a slower innitely variable rate to rotate the-tool, creating constant rotational slippage in said medium throughout 3601degree relative rotation of the drive and drill whereby lthe tool during drilling is maintained free for rotational pulsing, advancing the tool into the work metal, and axially supporting the tool independently .of the work metal.

16. The method of advancing a drilling tool Vthrough a body of metal, that includes forming comminuted chiplike cuttings and a hole that is burr-free at the drill exit end by creating a rotational drive, transmitting the drive to the tool through a rotationally yielding :fluid medium and at a slower innitely variable rate within a range of about 70% to 90% of the rotational drive speed, creating constant rotational slippage in said medium throughout 360 degree relative rotation of the .drive and drill whereby the tool during drilling is maintained free for rotational pulsing, advancing the tool into the Work metal, and axially supporting the tool independently of the work metal.

References Cited in the tile Aof this patent UNiTED STATES PATENTS 1,994,772 Landriani Mar. 19, 1935 2,759,580 Bower Aug. 2l, 1956 2,807,176 Butcher et al Sept. 24, 1957 FOREIGN PATENTS 198,473 Great Britain June 7, 1923 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,89%26 June 239 1959 Earnest EN Martin et al.

It is hereby certified that error appears in the'printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

and column 7, lines l29 24, 35,9 and column 8, line reed e= tool cm; column '7, linesl, 24,

each occurrence, reed cutting mo Column 6, line l0, ZH, for "drill", each, occurrence, 36, and column 8, line 5 for "drilling",

Signed and sealed this lth @agi of November 1959..

(SEAL) Attest:

KARL EL, AXLTNE ROBERT C. WATSON Commissioner of Patents Attesting Officer 

